Signal transmission line



1935- I A. R. RIENSTRA 2,010,644

SIGNAL 'l'RAIISM]:SSIONv LINE Filed Aug. 25, 1935 INVENTOR. ARR/ENSTRAATTORNEY r a geometric progression to four decibels.

Patented Aug. 6, 1935 UNITED STATES PATENT OFFICE SIGNAL TRANSMISSIONLINE Application August 23, 1933, Serial No. 686,354

17 Claims;

, control circuits at a repeater station on a transmission line with aplurality of pairs of relays controlled according to the energy level ofthe signals on the line that shall effect functions in number accordingto a geometric ratio in controlling attenuation pads to govern the gainat the repeater station.

A further object of the invention is to provide a repeater station on atransmission line with a number of attenuation pads increasing inattennation-in a geometric progression and a number of pads having equalattenuation and with a plurality of pairs of control relays that shallefiect functions in number according to a geometric ratio in controllingthe attenuation pads to govern the gain at the repeater station.

In the transmission of signals over a transmission line changes in theattenuation of the transmitting medium are caused by changes indifferent conditions as, for example, changes in the weather. In orderto obtain good transmission of the signals, correction must be made forthe changes in attenuation of the transmitting medium so as to maintainthe transmission -equiv-.

alent of the line substantially constant.

In accordance with the present invention all or a number of the repeaterstations on a trans mission line are provided with attenuation pads forcontrolling the gain. The attenuation of a number of the pads at eachrepeater station in.

creases in accordance with a geometric progression and a number ofthepads have equal attenuation. In the circuits employed for describingthe invention, eight attenuation pads are provided. The attenuation ofthe first five pads increases from a quarter decibel attenuation by Eachof the last three attenuation pads have an attenuation of four decibels.

The attenuation pads are directly controlled by a series of pad relays,one relay beingprovided for controlling each attenuation pad. Thecircuits for operating the pad relays are partially completed by meansof a plurality of pairs or control relays. The control relays areoperated in accordance with the energy levelof the signals or a pilotcurrent on the transmission line. The

operating circuits for the pad relays are completed by means of a timerelay which is energized and operated at regular intervals.

The pairs of control relays are arranged to effect functions in numberaccording to a geometric ratio. Moreoventhe relays in each pair operateand release in a fixed sequence. A high level relay and a low levelrelay which are oper ated in accordance with the energy level of thecurrents on the transmission line are provided for governing theoperation of the control relays. For each operation of the high levelrelay or the low level relay the first pair of control relays is eitheroperated or released. For every other operation of the high level relayor the low level relay the second pair of control relays is eitheroperated or released. The remaining control relays operate in a likemanner. The high level relay and the low level relay may be controlledby a pilot current on the transmission line or 2 may be controlled bythe signal currents. The signal currents'may be within the voicefrequency range or may be carrier currents having a much higherfrequency range.

If all the attenuation pads are out of the transmission line and theenergy level of the signals on the line is above normal, the high levelrelay is operated for effecting operation of the first pair of controlrelays. The first pair of control relays prepares a circuit foroperating the first 0 pad relay. The circuit for operating the first padrelay is completed by the timing relay for inserting the quarter decibelpad in the line. If the energy level of the signals on the line is notcorrected by the first pad the high level relay is again operated andthe second one half decibel pad is inserted in the line and the quarterdecibel pad taken out of the line. Such operation of the controlcircuits continues until the correct attenuation is inserted in theline. I! the energy level 49 of the signals on the line fallsbelownormal, the low level relay is operated for withdrawing impedance fromthe line by quarter decibel steps.

If the attenuation range of the pads is insufficient to correct theenergy level of the signals, an alarm is sounded.

The single figure in the accompanying draw-' ing is a diagrammatic viewof control circuits located at a repeater or terminal station andconstructed in accordance with the invention.

Referring to the drawing a repeater station on a transmission linecomprising conductors l and 2 is provided with attenuation pads A1, A2,A3; A4, A5, A6, A7 and A8. The pads A1 to A5, inclusive, in crease inattenuation according to a geometric progression. Pad A1 has one quarterdecibel attenuation and the pad As has four decibels attenuation. Thepads A6, A7 and As each have four decibels impedance. A plurality of padrelays L1, L2, L3, L4, L5, L6, L7 and L3 are provided for inserting andexcluding the attenuation pads in and from the line circuit. The padrelay L1 is provided with armatures 3, t and 5. The relay L2 is providedwith. armatures 5, l and 8. The relay L3 is provided with armatures 9,iii and H. The relay L4 is provided with armatures i2, IS and it. Therelay L5 is provided with armatures i5, l5 and ii. The relay L6 isprovided with armatures i 8, i9 and 28. The relay L1 is provided witharmatures 2i, 22 and 23. The relay L3 is provided with armatures 24, 25and 26.

A plurality of pairs of control relays Z1 to Z7, inclusive, and W1 to W1inclusive, are provided for governing the operation of the pad relays L1to L3, inclusive, to control the attenuation in the line circuit at therepeater station. The control relays are governed in accordance with theenergy level of a pilot current at the repeater sta-v tion.

v The pairs of control relays effect functions in number according to ageometric ratio. The term function as used in the specificationisintended to cover the operating or the releasing of a relay. The-pairof relays comprising relays Z1 and W1 operate cr release every time achange is made in the arrangement of attenuation pads. The second pairof control relays comprising the relays Z2 and W2 either operate orrelease every other time a change is made in the arrangement ofattenuation pads. The third set of control relays comprising the relaysZ3 and W3 function every fourth time. a change is made in thearrangement of attenuation pads. The remaining pairs or control relaysoperate in a like manner according to the geometric ratio. It isunderstood inserted in the line or continuously withdrawn from the lineand not inserted and withdrawn armatures 30, Si, 32 and 33. A movablecontact member Stis controlled by the armature 3| of the relay W1. Therelay Z2 is provided with armatures 35, st and 37. The relay W2 isprovided witharmaturestt, 39, ii) and 4!. A movable switch member Q2 iscontrolled by the armature 39 of the relay 42; The relay Z3 is providedwith armatures 3 54 and 55. The relay W3 is provided witharmatures 36,61, 48 and 3. A movable-switch memberfiil is controlled by the arma-'ture 4i and the relay W3. The relay Z is provided witlrarmatures Si, 52and 53. The relay W4 is provided with armatures 5 5, 55, 56 and 5''.Amovable switch member 58 is controlledby the armature of the relay W4.The relay Z5 is provided with armatures 59, Bil and 6 l The relay W5 2is provided with armatures 62, 63, 64 and 65. A movable switch member 86is controlled by the armature 53 of a relay W5. The relay Z6 is providedwith armatures 61, $8, 69 and. iii. The relay We is provided witharmatures 713, it and :1 :5. A movable switch member '55 is controlled.by

The pairs of control relays are governed in accordance with theoperation of a galvanometer 83 which is connected to the line conductorsl and 2 by means of a filter 8: 1 and a rectifier 89. The filter B l isselective of the pilot current employed for controlling the gain at therepeater stations. The galvanometer 83 operates a pointer 85 above highcontact members H and low contact members L.- If the energy level of thepilot current on the line is above normal, the galvanometer arm 85 willbe over the contact members H and if the energy level of the pilotcurrent on the line is below normal, the arm 85 of the galvanometer willbe positioned above the contact members L. A constant speed motor 8% ofany suitable type has two cam members 8'2 and 88 mounted on the armatureshaft thereof. The cam member 8? closes timing contacts T at regularintervals. The cam member 88 engages a lever 98 having an arc-shapedportion Sta positioned above the arm 85 of the galvanometer 83. Thelever S13 is pivotally mounted so that each time the cam member 88 isoperated the arc shaped portion 9 ia thereof is moved downwardly andengages the arm 85 of the galvanometer 83. When the arm 85 of thegalvanometer 83 is moved downwardly, contacts H or contacts L are closedif the arm is positioned above either of said contacts. The cam members8'! and 88 are so positioned on the armature shaft of the motor 86 thatthe contact members T are-never closed at the same time the contactmembers H or the contact members L are closed.

The T contacts when operated by the cam member 81 complete a circuitfrom battery 92 for energizing the time relay 9 i. The time relay 9| isprovided with an armature 93 which controls a movable grounded contactmember 96. The time relay 9! serves to complete circuits partiallycompleted by the control relays for operating the pad relays. 1 r

The low level contact members L when closed with a relay 95 operatedcomplete a circuit from a battery 96 for operating a loW level relay 9?,If the relay 95 is released when the low level contacts L are closed, acircuit is completed for operating an alarm 99. The relay 95 isenergized from a battery 99 whenever any of the W relays are operated.The low level relay 97 is provided with an armature lflt.

The high level contact members H when closed with a relay it! operatedcomplete a circuit from battery ear 'for operating the high level relayThe high level relay m3 is provided with an armature i i. If thecontacts H are closed when the relay MM is released, a circuit iscompleted for operating the alarm 23. The relay to! is energized from abattery 5% whenever any of the W relays are in released position.Assuming all pads A1 to A3, inclusive, to be on of the line,all relaysto be deenergized except the relay it! which is operated whenever a Wrelay is released and the H contacts to be closed by the galvanometer 83and the cam member 88, a circuit is completed from the battery 602- turnto the armature 594. The relay W1 is operated and the armature 3icompletes a circuit from the battery 01 for holding the relay W1 inoperative position. The armature 39 of the relay W1 completes a circuitfrom battery $9 for operating the relay 95. The relay 95 is operated atthis time so that the low level relay 01 may be operated at any time theL contacts are closed for reducing the attenuation in the line.

q'lhe Z1 relay is not operated at the same time 535 as. the W1 relaybecause both terminals of the coil of the Z1 relay are grounded. Whenthe cam member 08 operates the lever 90 for opening the H contacts thecircuit energizing the high level relay I03, is opened. Relay. I03 isreleased 10; and the ground applied to the right terminal of the Z1relay is removed. The Z1 relayis then operated by a circuit extendingfrom ground through the armature 3 I, switch member 34, coil of therelay Z1, battery C1 and ground return to The armaturefl of the Z1 rethearmature 3|.

lay prepares a circuit from battery B1 for operating the L1 relay. Thearmatures 28 and 29 of the Z1 relay complete no circuits at this time.The

time contacts T are then closed by the operation -15 of the cam member81. The closing of the contact members T completes a circuit from thebattery 92 for operating the time'relay 9|. The time relay 9| completesa circuit for operating the L1 relay to insert the pad A1 in the line.The

circuit completed by the time relay 9| extends from grounded battery B1through a coil of the L1 relay, armature 21 of the Z1 relay, armature 93ofv the time relay, contact member 94 and ground return to the batteryB1. The armature 3 3 of the L1 relay completes a holding circuit fromthe battery B1 for the L relay when-the time relay 9| is released. 1 Thearmatures 4 and 5 of the L1 relay insert the quarter decibel pad A1 inthe line circuit.

I04. The W1 relay releases and completes a circuit for operating the W2relay. The circuit for operat ing the W2 relay may be traced from thearmature I04 through armature 32 of relay W1, armature 29 of, relay Z1,contact member 42, coil of the relay W2, battery C2, and ground returnto the armature I04. The relay Z2 does not operate at this time inasmuchas both terminals of the coil thereof are connected to ground. Uponrelease 5 11,; of theI 03 relay when the H contacts are opened, therelay Z2 is operated by a circuit extending from the battery C2 throughthe coil of the Z2 relay, contact member 42, armature 39 of the W2 relayand ground return to the battery C2. At this c. time a holding circuitfor the W2relay extends from the battery C2 through the coil ofthe W2relay, contact member 42, armature 39 and ground return to the batteryC2. When therelay I03 is released, Z1 relay is released because groundis removed from the terminal of the operating coil therefor. The releaseof the Z1 relay insures the release of the L1 relay when the timerelay9| is next operated. When the L1 relay is released the quarter decibelpad A1 is removed from the line.

The operation of the Z2 control relay prepares a circuit from battery B2for operating the L2 relay to insert the one half decibel pad A2 in theline. The operation of the time relay! I by the T contacts opens thecircuit of the L1 relay and com- ?:J'pletes a circuit for operating theL2 relay. The circuit completed by the armature 93 of the time relay 9|extends from the battery B2 through a Y coil of the L2 relay, armature35 of the Z2 relay, armature 93 of the time relay 9|, switch member :3and ground return to, the battery B2. The re.-

If the energy level of the signals on the line is lay L2 when operatedinserts the half decibel pad A2 in the line. The release of the relay L1removes the half decibel pad A1 from the line so that the attenuation inthe line has been increased by one quarter decibel.

Assuming the energy level of the line to fall below normalwhen therelays Z2, W2 and L2 are operated and the one half decibel pad A2 is inthe line, then the L contacts are closed for reducing the attenuation inthe line. The closure of the L contacts completes a circuit from thebattery 98 for operating the low level relay 9?. The armature I00 of therelay 91 completes a. circuit from the battery C1 for operating the W1relay. The circuit for operating the W1 relay extends from thebattery'Ci through the coil of the W1 relay, switch member 34, armatureI00 of the relay 9! and ground return to the battery C1. The Z1 relay isnotoperated at this time because ground is connected to both terminalsof the energizing coil thereof. The-armature 33 of the W1 relaycompletes a circuit for applying ground to the right terminal of the W2relay which releases. The release of the W2 relay does not open theholding circuit for the Z2 relay. The holding circuit for the Z2 relayis opened upon release of the relay 9?. The Z1 relay is operated uponrelease of the relay 91. The relay 91 is released by separation of the Lcontact members.

The operation of the Z1 relay prepares a circuit by operation of thearmature 21 for operating the L1 relay. The next operation of the timerelay 9| by the time contacts T opens the holding circuit for the relayL2 which releases and completes an operating circuit for the L1 relay.The L1 relay upon operation inserts a quarter decibel pad A1 in the lineand the L2 relay when released with draws the half decibel pad from theline. Thus, the attenuation of the line has been reduced by a quarterdecibel step.

Assuming the Z2 relay and the W2 relay to be operated'and the halfdecibel pad A2 to be in the line and the H contact members to be closedby reason of the energy level on the line being above normal, the highlevel relay IDS is operated. The operation of the relay I03 operates theW1 relay, the Z1 relay and the L1 relay in the same manner as describedwhen assumption was made that no pads were in the line and the Hcontacts were closed. When the Z1 relay and W1 relay are operated'andthe time relay 9| is operated by the T contacts, then a circuit iscompleted for operating the L1 relay which inserts the quarter decibelpad A1 in the line. At this time the Z2, W2 and L2 relays are operatedand the half decibel pad A2 is in the line. 1 Assuming the Z1, W1, Z2,W2, L1 and L2 relays to be operated and the energy level on the line tobe above normal so that the H contacts are again closed, the high levelrelay I03 is operated. The armature I04 01? the relay I03 applies groundto the right terminal of the energizing coil of theW1 relay whichreleases. The release of the W1 relay applies ground from the armatureI04 of the relay I03 through armature 32 of the relay W1, armature 29 ofthe relay Z1 and armature 36 of the relay Z2 to the upper terminal ofthe relay W2. The relay W2 then releases. The release of the relay W2completes a circuit from the armature I04 through the armature 40 of therelay W2, armature 31 of the relay Z2, contact member 50, the coil ofthe W3 relay, battery C3 and ground return to the armature 04. The relayW: is operated. The relay Z3 is not operated at this time because bothterminals of the coil thereof are connected to ground. ,When the relayW3 is deenergized by separation of the H 7 contacts, the Z1 and the Z2relays are released by breaking of the circuits from batteries C1 andC2, through the operating coils of the Z1 and Z2 relays. The Z3 relayis'energized at this time by a circuit extending from the battery C3through the operating coil for the relay Z3, contact member 50, armaturell and ground return to the battery C3. The armature A3 of the Z3 relayprepares a circuit from the battery B3 to operate the L3 relay. Thecircuit for operating the L3 relay is completed by the time relay 9!when the T contacts are closed. The circuit for operating the L3 relayextends from the battery B3 through coil of the L3 relay, armature 43,armature 93, contact member 9t and ground return to the battery B3. Therone decibel pad A3 is inserted in the line upon operation of the L3relay. The time relay 8i not only operates the L3 relay for insertingthe A3 pad in the line, but also releases the L1 and L2 relays forWithdrawing the A1 and A2 pads from the line.

If the energy level of the signals on the line is still above normalvalue with the A3 pad in the vline and the Z3 and W3 relays operated,the H contacts are again closed for operating the high level relay l Therelay N13 when'operated under the above conditions effects operation ofthe Z1 and W1 relays in the manner above set forth. The Z1 relay whenoperated prepares a circuit for operating the L1 relay which is operatedupon operation of the time relay 9! by the time contacts T. The L1 relayinserts the A1 pad in the line with the A3 pad.

If the H contacts are again closed at this time the relay m3 is operatedfor efiecting operation of the Z2 relay and the W2 relay and the releaseof the Z1 relay and the W1 relay. The Z2 relay prepares a circuit foroperating the L2 relay so that upon operation of the time relay 9| bythe T contacts, the L2 relay is operated and the L1 relay is released.The operation of the L2 relay adds the A2 pad in circuit with the A3 padand the release of the L1 relay withdraws the A1 pad from the line. TheA2 and the A3 pads in the line have an attenuation of one and one halfdecibels.

If the H contacts are again closed by reason 01 the energy level of thesignals on the line being above normal, the high level relay N33 isagain operated for efifecting operation of the Z1 and the W1 relays inthe manner above set forth. The Z2, W2 and the Z3 and the W3 relays aswell as the L2 and L3 relays are held in an operated position at thistime. The Z1 relay prepares a circuit for operating the L1 relay. Thetime relay 9i operated by the T contacts completes the operating circuitfor the L1 relay for operating the L1 relay to insert the A1 pad in theline. At this time the A1. A2 and A3 pads are on the "line so that theattenuation of the pads in the lineis one and three-quarters decibels. VI

If the H contacts are again closedby reason of the high energy level ofthe line, the high level relay the is operated. The armature of the highlevel relay G3 places aground upon the upper terminal of the relay W1 sothat the relay W1 releases. pletes a ground circuit for the right,terminal of the W2 relay which extends from the armature its through thearmature 32, armature 29 and armature 3 5 to the right terminal of therelay W2.

The W2 relay upon releasing connects a ground.

circuit to'the right terminal of thecoil for the W3 relay. The circuitconnecting ground with the right terminal of the W3 relay extends fromThe release of theW1 relay comthe grounded armature 104 through armature40 of the relay W2, armature 31 of the relay Z2 and armature M of therelay Z3 to the right terminal of the coil of the W3 relay. The relay W3upon releasing completes a circuit for operating the W4 relay. Thecircuit for operating the W4 relay extends from battery C4 through thecoil of the W4 relay, contact member 58, armature 45 of the Z3 relay,armature 48 of the W3 relay, armature I84 of the H33 relay and groundreturn to the battery C4. The W4 relay upon operation establishes aholding circuit for itself through the armature 55. The Z4 relay is notoperated atthis time because both terminals of the energizing coilthereof are connected to ground; When the high levelrelay 5% is releasedby separation of the contact members H, the Z4 relay is operated fromthe battery C4 through the armature 55 of the W4 relay. At the same timethe Z1, Z2 and Z3 relays are released. The Z4 relay prepares a circuitfor operation of the L4 relay. Upon operation of the time relay 9i theL4 relay is operated by a circuit extending from the battery B4 throughthe coil of the L4 relay, armature 5|, armature 93, contact member t4and ground return to battery B4. The operation of the L4 inserts the twodecibels pad A4 in the line. At the same time the operation of the timerelay 9! releases the L1, L2 and L3 relays to withdraw the A1, A2 and A3pads from the line.

If the H contacts are again closed the Z1, W1 andL1 relays are operatedfor inserting the quarter decibelpad A1 in the line. If the H contactsare again closed the Z2 and W2 relays are operated to insert the halfdecibel A2 pad in the line while the Z1, W1 and L1 relays are releasedto withdraw the quarter decibel pad A1 from the line. The next operationof the H contacts serves to operate the Z1, W1 and L1 relays to insertthe quarter decibel pad A1 in circuit with the A2 and A4 pads. The nextoperation of the H contacts operates the Z3, W3 and L3 relays to insertthe one decibel pad A3 in circuit with the two decibel pad A4, at thesame time the relays Z1, W1, Z2, W2, L1 and L2 are released to withdrawthe A1 and A2 pads from the line.

With the pads A3 and A4 in the line producing three decibel attenuationand the relays L3, L4, Z3, W3, Z4 and W4 operated, the contacts H areagain closed if the energy level on the line is above normal. The highlevel relay I03 is operated to insert the quarter decibel pad A1 in theline. The next operation of the high level relay 103 by the H contactsinserts the half decibel pad A2 in the line and withdraws the quarterdecibel pad A1. The next operation of the high level relay I63 by the Hcontact inserts the quarter decibel pad A1 in the line. At this time thepads A1, A2, A3 and A4 are in the line producing three and three-quarterdecibel attenuation.

'If the high level relay m3 is again operated by the H contacts, thecircuit grounded by the armature I84 of the relay Hi3 places ground onthe right terminal of the coil for the W1 relay. The W1 relay releases.The armature 32 of the W1 relay then effects release of the W2 relay.The armature MB of the W2 relay then effects release of the W3 relay.The W3 relay by means of its armature 48 effects release of the W4relay. Upon release of the W4 relay a circuit is completed through thearmature 56 for efiecting operation of the W5 relay. The W5 relay uponoperation completes a holding circuit from the battery C5 through thearmature 63.

The Z5 relay is not operated at this time inasmuch as a grounded circuitis connected to eachterminal of the coil of. the relay. Upon release ofthe I03 relay by separation .of the H contacts the relays Z1, Z2,

Z3 and Z4 arereleased and the Z5 relay is operated. The operation of theZ5 relay prepares a circuit from the battery B5, through the armature 59for operating. the L5 relay upon the next operation 01" the time relay9!. The operation of the time relay 9! by the T contacts releases the L1relay, the L2relay, the L3 relay and the L4 relay to withdraw the padsA1, A1, A3 and A4 from the line. The relay L5 is operated to" insert thepad A5 in the line.

The pad A5 inserts an attenuation of four decibels in the line. Therelays L5, Z5 and W5 are operated at this time. The next'operation ofthe H contacts effects operation of the Z1, W1 and L1 relays to insertthe A1 pad in circuit with the A5 pad. If the H contacts are againoperated by reason of high energy level on the line, the Z2, W2 and L2relays operate to insert the A2 pad in the line and the Z1, W1 and L1relays release to withdraw the A1 pad from the line. The next operationof the H contacts efiects operation of the Z1, W1 and L1 relays toinsert the A1 pad in circuit with the A2 and A5 pads. At this time fourand three-quarter decibels impedance is in theline. The next closureofthe H contacts effect operation of the Z3, W3 and L3 relays to insertthe A3 pad in the line and the release of theZ1, W1, L1, Z2, W2 and L2relays to withdraw the A1 and the A2 pads from the line. The nextclosure of the H contactseffects operation of the Z1, W1 and L1 relaysto insert the A1 pad in the line. The next closureof the H contactsefiect's operation of the L2, Z2 and W2 relays to insert the A2 pad inthe line and release of the Z1, W1 and L1 relays to Withdraw the A1 padfrom the line. The next operation of the H contacts 0 erates the Z1, W1and L1 relays to insert the A1 pad in circuit with the A2,'A'5 and A5pads. The next closure of the H contacts effects operation of the Z4,W4'and L4 relays to insert the A4 pad in the line and the release of theZ1, W1, L1, Z2, W2, L2, Z3, W3 and L3 relays to withdraw the A1, A2 andA3 pads from the line.

The next closure of the H contacts effects operation of the Z1, W1 andL1 relays toinsertthe A1 pads in the line. The next closure of the Hcontacts operates the Z2, W2 and L2 relays to insert the A2 pad in theline and the release of the Z1, W1 and L1 relays to withdraw the A1 padfrom the line. The next closure of the H contacts operates the L1, W1and Z1 relays to insert the A1 pad in the line. The next closure of theH contacts operates the Z3, W3 and L3 relays to insert the A: pad in theline and the release of the Z1, ,W1, L1, Z2, W2 and L2 relays towithdraw the A1 and the A2 pads from the line. The next closure of the Hcontacts operates the Z 1, W1 and the L1 relays to insert the A1'pad inthe line. The next closure of the H contacts operates the Z2, W2 and'L2relays to insert the A2 pad in the line to produce an impedance of sevenand threequarters decibels;

1 lease the W1 relay. The armature 32 of the W1 relayeffects release ofthe W2 relay. The arma ture 40 or the W2 effects the release of the W3relay. The armature 48 of the W3 relay ef fects release of the W4 relay.The armature 56 ofthe W4 relay effects release of the W5-relayi Uponrelease of the W5 relay, the armature 64 completes a circuitfor'operating the W6 relay from the battery 66. The circuit .foroperating the W6 relay may be traced from the battery 0'6 through thecoil of the W6 relay, contact member it, armature 6! of the Z5 relay,armature 84 of The Z6 relay is operated by.circuit from battery C6through the coil of the relay, contact members i 6, armature 13' of theW6 relay and ground return to the battery C6. Upon operation of the.relay 3!, the L1, L2, L2 and L4 relays are released to withdraw thepads A1, A2, A3 and A4 from the line. The'Ls relay is maintainedoperated and a circuit is completed for operating the L5 relay. The L5relay maintains the A5 pad in theline and the L6 relay inserts the A5pad in the line so that the attenuation in the line is'now eightdecibels. The circuit for operating the L5 relay. extends from thebattery B5 through a, coil of theiiLs relay, armature 3'! of the Z6relay, armature 9310f inclusive, and relays W1 to;W4, inclusive, toinsert the A1 to A4 pads in the linewith, the A -and A6 pads. With theA1 130,116 pads in the line, the impedance is eleven and tlneefluartersdecibels. The next operation of the H contacts in the customary mannerreleases the W1 relay which releases the W2 relay, the W2 relay releasesthe W relay, and the W3 relay releases the W4relay. Thearmature 56'ofthe W4 relay oompletesa circuit for operating the W5 relay. The circuitcompleted for -operating the W5 relay extendsfrom the battery C5 throughthe coil of thews relay, a contact member 66, armature 53 of the Z4relay, armature 55 of the W4 relay, armature we of the M3 relay andground return to the battery C5. The W5 relay is operated but the Z5relayis not operated until the release of. the l03.relay. The release ofthe sea relay effects releaseiof the Z1, Z2, Zgand Z4 relays. The Z5relay prepares a circuit for operating the L2 relay. Upon operation ofthe relay 9 I, by the time contacts T, the relays L1, L2, L3 and L4 arereleased to withdraw the pads A1, A2, A3 and A4 from the line; The L5,;and L6 relays are held in operated position by reason. of the Z6 beingheld operated. The L7 relay, is operated by. a circuit extending fromthe battery B7, armature iii of the relay Z6, armature 59 of the relayZ5, armature -93 ofthe time relaylil; contact member Stand ground returnto the ba tery B7. At this time the relays L5, L6 and L2 are operated toinsert the A A6 and A2 pads in-the line. The pads A5, A6 and A 1 havean=attenuation of 12 decibels. I V V I v If the H contacts are operatedcontinuously by reason of high energy level on the line with the A5, A6and A7 pads in the line, the A1, A2, A3 and A4 pads will be inserted inthe line by one quarter decibel steps as disclosed heretofore. ,When theA1 to A7 pads are inserted in the line, the L1 to L7 relays areoperated, the Z1 to Z6 relays are operated and the W1 to We relays areoperated. With the circuits in such condition the next operation of theH contacts energizes the H13 relay to release the W1 relay, the W1 relayreleases the W2 relay, the W2 relay releases the W3 relay, the W: relayreleases the W4 relay, the W4 relay releases the W5 relay and the W5relay releases the We relay. The armature M of the We relay completes acircuit for operating the W7 relay. The circuit for operating the W7relay extends from the battery. 07 through the coil of the W7 relay,cont-act member 8|, armature E9 of the Z6 relay, armature M of the Werelay, armature M of the H33 relay and ground return to the battery C7.The Z7 relay is not operated at this time by reason of both terminals ofthe coil thereof being grounded. The release of the relay I93 efiectsrelease of the Z1, Z2, Z3, Z4, Z5 and Z6 relays and effects operation ofthe Z7 relay. The circuit for operating the Z7 relay extends from thebattery C7 through the coil of the Z7 relay, contact member 8|, armature88 of the W7 relay and ground return to the battery C7. Operation of thetime relay 9| by the T contacts efiects release of the L1, L2, L3 and L4relays. The L5, L6, L7 and L8 relays are held operated by the circuitscompleted by the Z7 relay. The circuit for operating the L5 relay may betraced from the battery B5 through the coil of the L5 relay, contactmember closed by the armature 18 of the Z7 relay, armature 93 of thetime relay 9|, contact member 94 and ground return to the battery B5.The circuit for operating the Le'relay may be traced from the battery Bsthrough a coil of the relay Ls, armature 'll of the Z7 relay, armature93 of the time relay 9|, contact member 94 and ground return to thebattery B6. The circuit for operating the L7 relay may be traced fromthe battery B7 through the coil of the relay L7 armature ll of Z7 relay,armature 93 of the time relay 9|, contact member 94 and ground return tothe battery B7. The circuit for operating the L8 relay may be tracedfrom the battery Ba through the armature 18 of the Z7 relay, armature 93of the time relay 9|, contact member Q4 and ground return to the batteryB3.

The operation of the L5, L6, L7 and La relays inserts the pads A5, A6,A7 and A8 in the line to produce an attenuation of sixteen decibels. Itis apparent at this time that if so desired, the pads A1, A2, A3 and A4may be inserted in the line with the pads A5, A6, A7 and A3 to produce anineteen and three-quarter decibel attenuation. If all the pads A1 toAs, inclusive, are in the line and the H contacts are closed a circuitis completed for operating the alarm 88. The attenuation is withdrawnfrom the line under the control of the L contacts by one quarter decibelsteps in the same manner as the attenuation is added to modificationsare intended to be covered by appended claims.

' What is claimed is:

1. In combination, a plurality of pairs of control relays forcontrolling the gain at a station on a transmission line, means forinsuring the operation of the relays by pairs with the operation of therelays of each pair in a predetermined sequence and for insuring therelease of the relays by pairs with the release of the relays of eachpair in the same sequence, a pair of high level contact members, andmeans comprising circuits governed by said contact members forcontrolling said pairs of relays to effect functions the number of Whichcorrespond to a geometric progression.

2. In combination, a transmission line having a station, a plurality ofattenuation pads adapted to be inserted in the line for controlling thegain at the station, a number of said pads increasing in attenuationaccording to a geometric progression and a number of said pads havingequal attenuations, and means operated according to the energy level ofthe signals on the line for controlling said pads to change theattenuation at the station by equal attenuation steps.

3. In a signal transmission system, a transmission line, a plurality ofattenuation pads adapted to be inserted in the line for controlling theattenuation, a number of said pads increasing in attenuation in ageometric progression and a' number of said pads having equalattenuations and means comprising a plurality of sets of relaysefiecting functions the number of which correspond toa geometric ratiofor inserting said pads in the line by equal attenuation steps.

4. In combination, a transmission line having a station thereon, aplurality of attenuation pads for controlling the attenuation. at thestation, a number of said pads increasing in attenuation in a geometricprogression and the remaining pads having equal attenuations, a padrelay for controlling each pad, pairs of control relays for governingsaid pad relays, and means controlled according to the energy level of apilot current on the line for operating said control relays to governthe operation of said pad relays and adjust the attenuation in the lineat the station by equal attenuation steps.

5. In combination, a plurality of attenuation pads for controlling theattenuation on a transmission line, a number of said' pads increasing inattenuation in a geometric progression and the remaining pads havingequal attenuations, a pad relay for controlling the operation of each ofsaid pads, pairs of control relays controlling the operation of the padrelays, means for governing said control relays according to the energylevel of a pilot current on said line to prepare circuits for operatingsaid pad relays, said control relays effecting functions the number ofwhich correspond to a geometric progression when the attenuation ischanged by a number of steps in one direction, and means operated atregular time intervals for effecting operation of the pad relaysselected by saidcontrol relays.

6; In combination, a transmission line, a plurality of attenuation padsfor controlling the attenuation on the line, a pad'relay for controllingeach of said pads to govern the attenuation on the line, pairs ofcontrol relays for partially completing circuits to operate said padrelays, means for controlling said pairs of control relays to effectfunctions the number of which correspondto ageometric progression, meansfor effecting operating and releasing of the relays of each pair ofcontrol relays in a fixed sequence,

means comprising two pairs of contactmembers for governing the controlrelays'according to the energy level of a pilot current on, theline andmeans comprising a pair of contactmembers operated at fixed intervalsfor completing the? pad relay circuits partially completed by the pairsof control relays. l

7. In combination, a, plurality of; attenuation pads for controlling theattenuationEcm a trans-- mission line, a pad relay associated with-eachattemiation pad for controlling the insertion and withdrawal of 'thepads in and out of said line, a pluralityof pairs, of control relays forpreparing circuits to'operate said pad relays, means operated at regulartime intervals for effecting operation of 'the pad relays selected bysaid control relays, means for controlling said pairs: ofcontrol relaysto effect functions thereby the number of which correspond to ageometric progression, means for effecting functioning of the relays ofeach pair of control relays in a fixed sequence, and means forgoverning'the control relays according to the energy level of a pilotcurrent on the line.

8. In combination, a plurality of attenuation padsfor controlling theattenuation on a transmission line, a number of said pads increasing inattenuation in a geometric progression and a number of said pads havingequal attenuations, a series of pad relays for controlling the insertionand withdrawal of said pads in and out of said line, a plurality of setsof control relays for preparing circuits for operating said pad relays,said control relays effecting functions the number of which correspondto a geometric ratio when operated for inserting attenuation pads in theline, means for operating said control relays according to the energylevel at the repeater station of the currents on the line,-and meansoperated at regular time intervals for effecting operation of the padrelays selected by said control relays to change the attenuation byequal steps.

9. In combination, a plurality of attenuation pads for controlling theattenuation on a transmission line, apad relay for controlling each ofsaid pads to govern the line attenuation, a pair of control relays forcontrolling the operating circuit of each of said pad relays, means forcontrolling the pairs of said control relays according to the energylevel on the line, each operated pair of control relays partiallycompleting a circuit for operating the associated pad relay, and

,means operated at constant intervals for com plating the circuits ofthepad relays which have been partially completed by the pair of controlrelays.

10. In combination, a plurality of attenuation pads for controlling theattenuation on a transmission line, a pad relay for controlling each ofsaid pads to govern the line attenuation, a plurality of pairs ofcontrol relays for controlling the operation of the pad relays, eachpair of control relays when operated partially completing an energizingcircuit for a pad relay, means comprising high level contact members andlow level contact members for operating said pairs of control relaysaccording to the energy level on the transmission line, and meanscomprising timing contact members closed at fixed intervals forcompleting the energizing circuits of the pad relays which have beenpartially completed by the pairs of control relays and for releasing anyoperated pad relay when the pair of control relays associated therewithhas been released.

11. In combination, a transmission line, a repeatefstation on said line;a plurality of attenuation'padsfor controlling the gain at the repeate-r station, a pad relay for-controlling each of said pads,apluralityof pairs of cc trol rclays, each of said pairs oi relays wheerated serving to partially complete-an energizing cir. cuit for a padrelay, highlevelcontact members, low level contact members, means foroperating said high level contact'members when high enrgy level on saidlineto control said'pa relays and for operating'saidlow le v i memberswhen low energy level is orrsaid line to con-trol said pairs of relays,and means'comprising a pair of timing contact tin-em, s closed fixedintervals for completing the: Cirbuits pad relays which have beenpartially completed by the pairs of control relays. j M

12. In combination, two series of relaysdivided into pairs, each of saidpairs being formed by one relay from each series of relays, a pair ofcontact members, and means controlled by the oper ating and releasing ofsaid pair of contact members for controlling said series of relays sothat the pairs of relays effect functions the number 1 lays, a pair ofcontact members, and means comprising circuits controlled by the openingand closing of said contact members for operating the first pair ofrelays and for operating any other selected pair of relays bycontrolling the pairs of relays back of said selected pair of relays sothat the pairs of relays back of the selected pair of relays effectfunctions the number of which functions correspond to a geometricprogression.

14. In combination, two series of relays divided into pairs, each ofsaid pairs of relays being formed by one relay from each series ofrelays, a pair'of high contact members, a pair of low contact members,means comprising circuits controlled by said high contact members foroperating the first pair of relays and for operating any other selectedpair of relays by controlling the pairs of relays back of said selectedpair of relays so that the pairs of relays back of the selected pair ofrelays effect functions the number of which functions correspond to ageometric progression and controlled by said low contact members forreleasing the first pair of relays if operated alone and for releasinganother pair of operated relays by controlling the pairs of relays backof the operated pair of relays so that the pairs of relays back of theoperated pairs of relays effect functions the number of which functionscorrespond to a geometric progression.

15. In combination, a transmission line, a plurality of attenuation padsfor controlling the attenuation on the transmission line, a number ofsaid pads increasing in attenuation according to a geometric progressionand a number of said pads having equal attenuations, means comprisingpairs of control relays for controlling said attenuation pads to adjustthe attenuation of the line by equal attenuation steps, and means forcontrolling said pairs of control relays to effect functions the numberof which functions rality of attenuation pads for controlling theattenuation on the transmission line, a number of said pads increasingin attenuation according to a geometric progression and a number of saidpads having equal attenuations, a pad relay for controlling each of saidpads, a plurality of pairs of control relays for controlling theoperation of said pad relays, each pair of control relays when operatedpartially completing an energizing circuit for a pad relay, meanscontrolled by the energy level on said line for controlling said pairsof control relays to effect functions the number of which functionscorrespond to a geometric progression, and means comprising a pair oftiming contact members operated at fixed intervals for completingenergizing circuits for the pad relays that have been partiallycompleted by the pairs of control relays.

7 17. In combination, a transmission line, a repeater station on saidline, a plurality of attenuation pads for controlling the gain at therepeater station, pairs of control relays for controlling saidattenuation pads, a pair of high level contact members, a pair of lowlevel contact members, means for operating said high level contactmembers in case of high energy level on said line and for operating saidlow level contact members in case of low energy level on said line, andmeans comprising circuits controlled by the high level contact membersin case of high energy level on said line and by the low level contactmembers in case of low energy level on said line for effecting functionsby said pairs of relays the number of which functions correspond to ageometric progression.

ALBERT R. RIENSTRA.

